Inhibiting corrosion of copper-and zinccontaining metals in contact with aerated solutions of polyphosphate salts



United States Patent 3,252,914 INHIBITING CORROSION OF COPPER- AND ZINC-CONTAINING METALS IN CONTACT WITH AERATED SOLUTIONS OF POLYPHOSPHATESALTS This invention relates to new and useful improvements ininhibiting the corrosion of copper-containing and zinccontaining metalsin contact with aerated solutions containing polyphosphate salts, andmore particularly to a novel detergent composition containing acycloalkanoneaminobenzothiazole reaction product as a corrosioninhibitor.

Many surfaces are easily oxidized and corroded by contact with aeratedaqueous solutions but usually can be protected by the incorporation ofcorrosion inhibitors in the solution. Various organic chemicals havebeen used as corrosion inhibitors for aerated solutions, such as amines,mercaptans, heterocyclic nitrogen compounds, substituted ureas andthioureas, etc. Commercial detergent compositions, however, havepresented an especially severe problem because of their polyphosphatecontents. The polyphosphates which are included in most detergentcompositions tend to dissolve copper and zinc when contacted with thosemetals, either alone or in the form of their alloys such as galvanizediron, brass, bronze, etc. When aerated aqueous solutions containingpolyphosphates are contacted with copperor zinc-containing metals, thereis a tendency for the metals to go into solution as metal-polyphosphateanions. Because the detergents prevent the deposition of protectivefilms on the metal surfaces, little success has been realized heretoforein combatting the corrosiveness of aqueous detergent solutions.

It is therefore one object of this invention to provide a new andimproved method for inhibiting the corrosion of copperandzinc-containing metals when contacted by aerated solutions containingpolyphosphate salts.

Another object of this invention is to provide a new and improveddetergent composition containing a novel corrosion inhibitor forpreventing corrosion of copperand zinc-containing metals bypolyphosphates in the detergent.

A feature of this invention is the provision of an improved process forinhibiting the corrosion of copper and zinc-containing metals in contactwith aerated solutions containing polyphosphate salts'wherein there isadded to the solution about 0.005 to 0.20% wt. of a solution of thereaction product of a cycloalkanone and an aminobenzo thiazole.

Another feature of this invention is the provision of an improvedaqueous detergent solution containing watersoluble polyphosphate saltsand from about 0.005 to about 0.20% wt. of a solution of the reactionproduct of a cycloalkanone and an aminobenzothiazole, suflicient toinhibit corrosion of copperand zinc-containing metals when contacted bythe solution.

Other objects and features of this invention will become apparent fromtime to time throughout the specification and claims as hereinafterrelated.

This invention is based upon our discovery that the corrosion ofcopper-containing and zinc-containing metals by aerated detergentsolutions containing polyphosphate salts can be inhibited by adding tothe solution (either separately or together with the detergent) a smallamount, in the range of about 0.005 to 0.20% wt. of a solution ofPatented May 24, 1966 the reaction product of a cycloalkanone and anaminobenzothiazole.

The reaction products which are used as corrosion inhibitors inaccordance with this invention are prepared by mixing and heating anaminobenzothiazole and a cy cloalkanone, or by reaction of acycloalkanone with thiourea under acidic conditions. Theaminobenzothiazoles used in the preparation of our corrosion inhibitorhave the generic formula:

S a A I C-NH:

is a benzene or partially hydrogenated benzene nucleus, and R is loweralkyl or aryl; the cycloalkanones which are reacted with theamino-benzothiazoles to produce the novel corrosion inhibitors include C-C3 alkanones and alkyl and aryl derivaties thereof, such ascyclobutanone, cyclopentanone, cyclohexanone, cycloheptanone,cyclooctanone, cyclononanone, cyclodecanone, methylcyclopentanone,methylcyclohexanone, phenylcyclohexanone, benzocyclohexanone, etc. Thecycloalkanones which can be used also include condensed derivatives ofthe cycloalkanones produced by acidic condensation, e.g., 2-cyclohexylidenyl cyclohexanone, Z-cyclopentylidenyl cyclopentanone,2-cycloheptylidenyl cycloheptanone, etc.

A preferred method of preparation of these corrosion inhibitors is toreflux an aminobenzothiazole with a cycloalkanone for a period of about.1 to 3 hours to produce a syrupy reaction product. The reactants arepreferably added in stoichiometric portions in accordance with thereaction,

where is a cycloalkanone or substituted cycloalkanone.

Alternatively, certain of the corrosion inhibitors used herein can beprepared by essentially a one-step process by reaction of acycloalkanone such as cyclohexanone with thiourea under acidicconditions. Under these conditions, a reaction takes place whichproduces a hydrogenated derivative of the thiazole-cycloalkanonereaction product, which in some cases contains a cycloalkylidinesubstitue-nt on the cycloalkanone portion of the reaction product. Ingeneral, the reaction products which are used as corrosion inhibitors inaccordance with this invention are mixtures containing as an activeingredient at least one compound selected from the group consisting of:

W H H: N

is a radical selected from the group consisting of C -C cycloalkylideneradicals and condensed derivatives thereof containing a C -Ccycloalkylidene sub-stituent, and lower alkyl and aryl derivativesthereof.

The following non-limiting examples are illustrative of the scope ofthis invention.

and

where Example I The effectiveness of our corrosion inhibitor has beendemonstrated by a series of experiments with aqueous solutions of acommercial detergent containing mixed aryl alkyl sulfonates, sodiumtripolyphosphate, sodium sulfate, and other components. The detergentused in these experiments is a household detergent sold under thetrademark Tide (product of Procter and Gamble, Inc.). First, a watersolution of Tide was prepared in a concentration of 0.5 g. per 100 ml.water and divided into two flasks. Into one of the flasks there wasadded a sufiicient amount of the reaction product of cyclohexan-one and2-amino-4,5,6,7-tetrahydrobenzothiazole to achieve a concentration of0.1 g. per 100 ml. of solution. Then, two brass strips inch x 3 inches)were immersed in the solution in each flask and air was bubbled throughthe solutions at a rate of 20-30 mL/min. for a period of 72 hours whilethe temperature was maintained at 70 C. The weight losses from the brassstrips were as follows:

and

1 Average of two coupons.

From these experiments it is seen that the corrosion inhibitor used withthe detergent resulted in the reduction of more than 99% incorrosion-rate.

Example II To 15.2 g. of thiourea and 4 g. of hydrochloric acid wasadded 42 cc. of cyclohexanone. The mixture was refluxed for 3 hours andthe product poured into warm aqueous ethanol. The crystalline materialwhich appeared in 3 or 4 hours was filtered and dried. When thisreaction product is added to a detergent solution containingwater-soluble polyphosp-hate salts in a concentration of the additive inthe range of about 0.005% to 0.20% wt. of the solution, the rate ofcorrosive attack of the solution on copperand zinc-containing metals isdecreased by about Example Ill To 25 g. of Z-aminobenzothiazole is added30 cc. of cyclohexanone. The mixture is refluxed for 3 hours. Excesscyclohexanone is then removed by distillation leaving the product readyfor use. The product obtained consists essentially of:

When this reaction product is incorporated into an aqueous detergentsolution containing water-soluble polyphosphates in an inhibitorconcentration in the range from about 0.005 to 0.20% wt. of thesolution, the corrosivity of the solution toward zinc and coppercontaining metals is reduced by more than 90%.

Example IV To 30 g. of Z-aminobenzothiazole is added 90 cc. ofcyclohexanone and 4 g. of hydrochloric acid. The mixture is refluxed for3 hours and excess cyclohexanone and acid are removed by distillation.The product obtained consists mainly of:

When this reaction product is incorporated into an aqueous detergentsolution containing water-soluble polyphospha-tes in an inhibitorconcentration of 0.005 to 0.20% wt. of the solution, the tendency of thesolution to corrode copperor zinc-containing metals is reduced by anamount in excess of 90%.

When other cycloalkanones are reacted with aminobenzothiazole (orhydrogenated derivatives thereof) reaction products are obtained withinthe scope of the general formula given above. Likewise, when othercycloalkanones are reacted with thiourea under acidic conditions, amixed reaction product is obtained contain ing compounds within thegeneral formula. When these reaction products are incorporated into anaqueous detergent solution containing water-soluble polyphosphates, inan inhibitor concentration in the range from about 0.005 to 0.20% wt. ofthe solution, the tendency of the solution to corrode copperandzinc-containing metals is decreased by more than 90%. While theelfectiveness of these corrosion inhibitors has been demonstratedprimarily in connection with aerated solutions, it should be noted thata similar corrosion-inhibiting effect is obtained in the absence ofaeration of the solution.

While we have described our invention fully and com pletely with specialemphasis upon several preferred embodiments of our invention, we Wish itto be understood pr-opertly or, privilege is claimed tare defined asfollows:

1. A method of inhibiting the corrosion of copperand zinc-containingmetals in contact with aqueous, aerated solutions of polyphosphate saltsin amounts conductive to corrosion which consists essentially of addingto the solution a small amount, in the range of about 0.005 to 0.20% wt.of the solution, of the reaction product of stoicliiometr-ic quantitesof a cycloal-kanone selected irom the group consisting of cyclobutanone,cyclopentanone, cyclohexanone, cycloheptanone, cyclooctanone,cyclononanone, cyclodecanone, methylcyclopentanone,methylcycloheX-anone, phenylcyclohexanone, benzocyclohexanone, 2cy-clohexylidenyl cycloerexanone, 2 cyclo pentylidenyl cyclopentanone,2-cycloheptylidenyl cycloheptanone, and an aminobenzothiazole selectedfrom the group consisting of and 2. A method in accordance with claim 1in which the reaction product is added in admixture with thepolyphosphate salts.

3. A method in accordance with claim 1 in which said reaction productincludes as an active ingredient at least one compound selected from thegroup consisting of:

H2 H: N

and

where 6 5. A method in accordance with claim 3 in which said activeingredient is 6. A method in accordance with claim 3 in which saidactive ingredient is 7. A method in accordance with claim 3 in whichsaid active ingredient is 8. An aerated aqueous detergent solution ofWater soluble polyphosph-ate salts in amounts conducive to corrosion,and a small amount, in the range from about 0.005 to 0.20% wt. of thesolution, of the reaction prodnot of stoichiometric quantities of acyclo alkanone selected from the group consisting of cyclobutanone,cyclopentanone, cyclohexanone, cycloheptanone, cycloactanone,cyclononanone, cyclodecanone, methylcyclopent-anone,methylcyclohexanone, phenylcyclohexanone, benzocyclohexanone,2-cyclohexy1ideny1 cyclohexanone, 2-cyclopentylidenyl cyclopentanone,Z-cycloheptylidenyl cyclo heptanone, and an aminobenzot'hiazole selectedtrom the group consisting of H- H i N/ and C-NH:

at least one compound selected from the group consisting of H: s H N=@H: N and where is a radical selected from the group consisting of2-cycl0- 12. The solution in accordance with claim 9 in whichhexylidenyl cyclohexylidene, 2-cyclopentylidenyl cyclosaid activeingredient is pentylidene, 2-cycloheptylidenyl cycloheptylidene,, C S Ccycloalkylidene and methyl, phenyl and benzo derivatives thereof. 5 H

10. The solution in accordance with claim 9 in which said activeingredient is N 13. The solution in accordance with claim 9 in whichsaid active ingredient is H2 s\ 1 s H;

m c-N= H \CN: H il H; N 15 N 11. The solution in accordance with claim 9in which sald acnve mgredlent 1s 20 References Cited by the ExaminerUNITED STATES PATENTS 2,238,651 4/1941 Keenen 252-394 XR H2 s 2,618,60311/1952 Schaeffer 2s2 -137 XR H2 2,618,605 11/1952 Schaeffer 2s2 137 \iH 25 3,062,612 11/1962 Boucher 252390 XR H H2 N i JULIUS GREENWALD,Primary Examiner.

W. E. SCHULZ, Assistant Examiner.

1. A METHOD OF INHIBITING THE CORROSION OF COPPER- AND ZINC-CONTAININGMETALS IN CONTACT WITH AQUEOUS, AERATED SOLUTIONS OF POLYPHOSPHATE SALTSIN AMOUNTS CONDUCTIVE TO CORROSION WHICH CONSISTS ESSENTIALLY OF ADDINGTO THE SOLUTION A SMALL AMOUNT, IN THE RANGE OF ABOUT 0.005 TO 0.20% WT.OF THE SOLUTION, OF THE REACTION PRODUCT OF STOICHIOMETRIC QUANTITITIESOF A CYCLOALKANONE SELECTED FROM THE GROUP CONSISTING OF CYCLOBUTANONE,CYCLOPENTANONE, CYCLOHEXANONE, CYCLOHEPTANONE, CYCLOOCTANONE,CYCLONANONE, CYCLODECANONE, METHYLCYCLOPENTANONE, METHYLCYCLOHEXANONE,PHENYLCYCLOHEXANONE, BENZOCYCLOHEXANONE, 2-CYCLOHEXYLIDENYLCYCLOEREXANONE, 2-CYCLOPENTYLIDENYL CYCLOPENTANONE, 2-CYCLOHEPTYLIDENYLCYCLOHEPTANONE, AND AN AMINOBENZOTHIAZOLE SELECTED FROM THE GROUPCONSISTING OF